The present invention relates to optical modulation and, more particularly, to the analog frequency modulation of an optical laser.
A great amount of research and development effort is being expended to develop high speed information lasers and optical fibers. The vast amount of this research effort is centered about digital modulation in the gigahertz range using optical fibers for transmitting the maximum distance without repeaters. The bulk of this digital transmission uses pulse code modulation (PCM). Much of the research effort is directed to modulators for PCM which involve the ability to switch transmitted light on and off at the high switching rates necessary. The maximum distance of transmission capability for digital modulation is limited by the abilitity of the detector to detect the presence and position of different pulses which have undergone smearing or dispersion during transmission through the fiber. Circuitry for accomplishing the modulation and detection of digital and analog modes are expensive and bulky, the modulators requiring the use of special crystals.
The motivation for the extensive development of the ability to modulate light for information transmission is due to the much higher carrier frequency of the light than radio or microwaves, and therefore light can be used to transmit information at much higher rates than these more conventional methods.
In this recent research and development work, modulation of light sources using standard analog modulation has been largely overlooked with the idea that digital transmission is noise immune and has greater reliability. However, the digital approach greatly increases complexity and cost of modulating and demodulating a light source.
Accordingly, it is desirable to provide a modulation of a light transmission system for transmission of information which is inexpensive, very compact, and is capable of the high bandwidths of miniature systems, e.g., greater than 1000 MHz.
Accordingly, it is an object of the present invention to provide an analog frequency modulatable laser for information modulation of a coherent light source at large bandwidths.
Another object of the present invention is to provide an analog frequency modulator laser wherein the radiation frequency of the laser is frequency modulated by change of the optical resonant cavity forming mirrors corresponding to encoded information.
Yet another object of the present invention is to provide an analog frequency modulated laser frequency of radiation of the laser is modulated by magnetostrictive means moving an optical cavity determining mirror.
Further objects and advantages of the presnt invention will become apparent as the following description proceeds and features of novelty characterizing the invention will be pointed out with particularity and to claims annex to and forming a part of this specification.